Cleaning method and cleaning apparatus, and electrophotographic photosensitive member and cleaning method of electrophotographic photosensitive member

ABSTRACT

The present invention provides a method for efficiently cleaning a cleaning subject, especially a method for cleaning an electrophotographic photosensitive member that enables a uniform and high quality image to be obtained without leaving image defects and irregular images, wherein the cleaning step of the cleaning subject comprises: making the circulation flow rate during dipping of a cleaning subject in the cleaning solution to be different from the circulation flow rate when the cleaning subject is pulled up; and showering the cleaning solution used in the cleaning step during the pull-up step on the surface of the cleaning subject; or wherein the method for manufacturing an electrophotographic photosensitive member for depositing a functional film by a plasma CVD method on an aluminum substrate containing silicon, iron and aluminum especially comprises cleaning steps of: degreasing oil components on the surface of the substrate prior to deposition of a film; making the circulation flow rate during dipping the substrate in the cleaning solvent to be different from the circulation flow rate when the substrate is pulled up; showering the cleaning solution to be used in the degreasing step on the surface of the substrate while the substrate is pulled up; and forming an Al—Si—O coating film using water containing an inhibitor in the rinsing step.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cleaning method and cleaningapparatus of a cleaning subject, and an electrophotographicphotosensitive member and a method for manufacturing the same. Thepresent invention especially relates to a cleaning method of opticalparts, electronic parts, mechanical parts and precision parts, and acleaning apparatus capable of cleaning the same, including anelectrophotographic photosensitive member and a method for cleaning theelectrophotographic photosensitive member comprising cleaning steps. Thepresent invention also relates to a cleaning method by which fats andoils, fatty acids and resins adhered on the surface of a cleaningsubject can be securely removed without using chlorinated solvents, andan apparatus to be used for these purposes.

[0003] 2. Description of the Related Art

[0004] The method for manufacturing a substrate for use in anelectrophotographic photosensitive member comprises the following steps.

[0005] The surface of a substrate for the electrophotographicphotosensitive member is machined to a flatness within a prescribeddegree by cutting with a diamond blade using a lathe or milling machine.The substrate subjected to surface machining is then cleaned with anaqueous solution of carbon dioxide, followed by depositing a film mainlycomposed of amorphous silicon to be converted into a deposition film ofa photoconductive material by applying a glow discharge decompositionmethod on the surface of the substrate. While materials such as glass,heat-resistant synthetic resin, stainless steel and aluminum areproposed for use in the material for the substrate of theelectrophotographic photosensitive member, metals are preferably usedfor the substrate material in most practical purposes, since metals areresistant to electrophotographic processes such as electrification,exposure, development, transfer and cleaning, thereby securing highpositional accuracy in order to maintain image quality. Aluminum is oneof the most suitable materials among them as a substrate for theelectrophotographic photosensitive member, because aluminum is ready formachining, cheap and lightweight.

[0006] Technologies related to the substrate material of theelectrophotographic photosensitive member are disclosed in U.S. Pat. No.4,702,981 and Japanese Patent Publication Laid-open No. 60-262936. U.S.Pat. No. 4,702,981 discloses a technology for obtaining an amorphoussilicon electrophotographic photosensitive member having good imagequality by using an aluminum alloy containing 2000 ppm or less of iron(Fe) as a supporting member. The patent publication also disclosesmanufacturing steps for forming amorphous silicon by glow dischargeafter applying a mirror machining by cutting a cylindrical substratewith a lathe. Japanese Patent Publication Laid-open No. 60-262936discloses an extrusion aluminum alloy being excellent in applying vacuumdeposition and containing 3.0 to 6.0 wt % of magnesium (Mg), in whichthe contents of impurities are suppressed to 0.3 wt % or less formanganese (Mn), less than 0.01 wt % for chromium (Cr), 0.15 wt % or lessfor Fe and 0.12 wt % or less for silicon (Si), with a balance of Al.

[0007] Technologies for applying a surface machining to form a lightreceiving layer on the surface of the substrate depending on theapplication field of the electrophotographic photosensitive member aredescribed in U.S. Pat. No. 4,735,883, and Japanese Patent PublicationLaid-open No. 62-95545. Although U.S. Pat. No. 5,480,754 proposes atechnology for cleaning the substrate with water, in which carbondioxide is dissolved, for preventing corrosion in the cleaning step withwater when an aluminum alloy is used for the substrate, no the processfor recycling the water used for cleaning, consequently no flow rate ofrecycling water, is described.

[0008] Japanese Patent Publication Laid-open No. 5-61215 discloses thesteps of circulating respective liquids in each cleaning vessel,continuously feeding a cleaning liquid into one vessel, allowing thecleaning liquid pooled in one vessel to overflow to transfer it toanother vessel, and cleaning the substrate in each vessel. However, nosteps for changing the circulation volume of water in the vessel inwhich the liquid overflows described.

[0009] While Japanese Patent Publication Laid-open Nos. 63-311261,1-156758 and 7-34123 disclose a technology for forming an oxide film onthe Al substrate, the step for circulating the cleaning water forrepeatedly cleaning the substrate is not described.

[0010] Meanwhile, a variety of materials such as selenium, cadmiumsulfide, zinc oxide and amorphous silicon, as well as organic substancessuch as phthalocyanine, are proposed in the technology of elementalmaterials to be used in the electrophotographic photosensitive member. Anon-crystalline deposition film represented by an amorphous silicon filmcontaining silicon atoms as principal components, or an amorphousdeposition film of amorphous silicon supplemented with, for example,hydrogen and/or halogen (for example fluorine and chlorine) has beenproposed as a high-performance, highly durable and non-pollutingelectrophotographic photosensitive member, some of which beingpractically used. U.S. Pat. No. 4,265,991 also discloses a technologyfor the electrophotographic photosensitive member whose photoconductivelayer is mainly composed of amorphous silicon.

[0011] Many methods such as a sputtering method, and methods fordecomposing material gases by heat (heat CVD method), light (light CVDmethod) and plasma (plasma CVD method) have been known in the art fordepositing non-crystalline films containing silicon atoms as principalcomponents as described above.

[0012] The plasma CVD method, by which the material gas is decomposed byplasma generated by a high-frequency or microwave glow discharge todeposit thin films on the substrate, is most suitable for depositing anamorphous silicon film for the electrophotographic photosensitivemember. Practical applications of these methods have been aggressivelydeveloped in recent years. Among the CVD methods, the plasma CVD methodadvantage of decomposition by microwave glow discharge, or the microwaveplasma CVD method, has been recently noticed as an industrial method fordepositing a film.

[0013] The microwave plasma CVD method is advantageous over othermethods in its high deposition rate and high conversion efficiency ofmaterial gases. One example of this microwave plasma CVD based on theadvantages as described above is described in U.S. Pat. No. 4,504,518.The patent described above discloses that a good quality deposition filmis obtained with a high deposition rate by the microwave plasma CVDmethod in a low pressure of 0.1 Torr (13.3 Pa).

[0014] A technology for improving the material gas conversion efficiencyby the microwave plasma CVD method is disclosed in Japanese PatentPublication Laid-open No. 60-186849. In the technology disclosed in thepatent publication described above, an inner chamber (or a dischargespace) is formed by disposing the substrate so as to surround anintroduction device of microwave energy to obtain a high conversionefficiency of the material gas.

[0015] Japanese Patent Publication Laid-open No. 61-283116 discloses animproved microwave technology for producing a semiconductor element.According to the technology disclosed in the patent publication above,an electrode (a bias electrode) for controlling plasma potential isprovided in the discharge space. Characteristics of the deposition filmare improved by depositing the film while controlling ion impact to thedeposition film by applying a desired voltage (a bias voltage) to thebias electrode.

[0016] However, there remain some problems to be solved in theelectrophotographic photosensitive member formed by the method asdescribed above. One problem is how to prevent abnormal growth in thedeposition film.

[0017] While abnormal growth portions are sometimes observed in thedeposition film grown on the substrate, the portions have a minute areaand possess insufficient surface charge. Generation of these abnormalgrowth portions is especially obvious in the amorphous silicon formed bythe plasma CVD method. Generation of such portions possessinginsufficient surface charge has been prevented by optimizing surfacemachining conditions, surface cleaning conditions and depositionconditions.

[0018] The following situations have been imposed on the technology:

[0019] 1) Definition of positive images has been improved in response tothe requirements for high image quality of the electrophotographicapparatus; and

[0020] 2) Electrification conditions have became severe as a result ofmaking copy machines high speed. Consequently, improvement of imagequality at the abnormal growth portions has been required since theportions possessing insufficient electric charges substantially have alarge influence on the peripheral potential.

[0021] The effect of abnormal growth on the image quality has been asmall matter since a conventional electrophotographic apparatus ismainly used for copying only printed letters in a typescript (so-calledline copy). However, since image qualities of the copy machine have beenimproved in recent years, copying many original documents containinghalf-tone images such as photographs is required. Therefore, forcomplying with these requirements, an electrophotographic photosensitivemember containing a small number of abnormal growth portions iscurrently required. Since the effect of the abnormal growth portions onthe image quality is more clearly visualized in the printed images incurrently spreading color copy machines, an electrophotographicphotosensitive member containing small number of abnormal growthportions is especially required.

[0022] The abnormal growth portions are so minute that localization ofthem is difficult even by a conductivity measurement using an electrode.When the photosensitive member is electrified, exposed and developed byintegrating the substrate having the deposition film containing theabnormal growth portions into an electrophotographic process using anelectrophotographic photosensitive member, especially when a uniformhalf-tone image is formed, images of a small potential differenceascribed to the abnormal growth portions on the surface of theelectrophotographic photosensitive member may be clearly visualized.

[0023] The effect of the abnormal growth portions on the image becomesespecially evident in the electrophotographic photosensitive membermanufactured by the plasma CVD method, as compared with a Seelectrophotographic photosensitive member manufactured by a vacuumdeposition method or an OPC electrophotographic photosensitive membermanufactured by a blade coating method or dipping method. However,productivity as well as repeatability of the plasma CVD method formanufacturing the electrophotograph are high, besides having wideapplicability since the film can be deposited by precisely adjusting itsthickness. Accordingly, highly efficient production of high qualitysubstrates is possible when the plasma CVD method is further improved.

[0024] Solar cells are another example of the device that can bemanufactured by the plasma CVD method other than the electrophotographicphotosensitive member. However, overall performance, or the overallphotoelectric conversion efficiency, of the solar cell is practicallynot affected even when the abnormal growth portions are finelydistributed at specific locations on the substrate, causing subtledifferences of the potential among the abnormal growth portions andother portions. Moreover, such practical problems as the quantity ofgenerated electricity may be solved and desired specification can beattained by post-treatment in the solar cell, even when a small numberof abnormal growth portions may exist. In the electrophotographicphotosensitive member, on the contrary, the presence of a small numberof abnormal growth portions as described above may affect the imagequality. Therefore, generation of the abnormal growth portions should beespecially prevented in the deposition step.

[0025] The second problem is to provide an effective cleaning methodusing an aqueous solvent. It has been desirable in recent years to avoiduse of chlorinated solvents from the view point of preservation of theenvironment, and the chlorinated solvents have been replaced by aqueoussolvents. However, oils and dusts floating on the surface of thecleaning liquid are liable to adhere again and contaminate the cleaningsubject after cleaning, when the cleaning subject is pulled up from thecleaning vessel after cleaning with the aqueous cleaning solvent.Accordingly, an effective cleaning method using the aqueous solvent isdesired, in order to efficiently wash the cleaning subject by enhancingthe ability for cleaning optical parts, electronic parts, mechanicalparts and precision parts and preventing the oils and dusts that havebeen once removed from adhering on the cleaning subject again.

[0026] The third problem is to prevent corrosion of the substrates bywashing with aqueous solvents. Especially when an aluminum substrate forthe electrophotographic photosensitive member as an example of thecleaning subject is washed with water, galvanic batteries are formedamong impurities and peripheral aluminum, where no impurities exist, atthe portions containing many impurities such as Si partially protrudingfrom the surface of the aluminum, accelerating corrosion of the surfaceof the substrate. While generation of corrosion has been prevented byusing an aqueous carbon dioxide solution as a cleaning solvent, a devicefor allowing carbon dioxide to dissolve in the cleaning solvent makesthe cleaning apparatus to be complicated and therefore cleaning cost isincreased. Accordingly, the construction of the apparatus should be moresimplified and the cleaning cost should be reduced.

[0027] The fourth problem is to suppress irregular cleaning along thelongitudinal direction from appearing when a long member along thelongitudinal direction such as the substrate of the electrophotographicphotosensitive member is pulled up from the cleaning solvent.

SUMMARY OF THE INVENTION

[0028] Accordingly, the object of the present invention is to provide amethod for effectively washing a cleaning subject. In more detail, theobject of the present invention is to provide a high performanceelectrophotographic photosensitive member containing a small number ofirregular growth portions and a method for manufacturing the same,wherein irregular cleaning of the substrate is suppressed whilepreventing corrosion of aluminum.

[0029] The foregoing objects can be attained by the following means. Thepresent invention proposes a cleaning method for enhancing cleaningability by effectively cleaning the cleaning subject, a cleaningapparatus, and an electrophotographic photosensitive member and a methodfor manufacturing the same.

[0030] In a first aspect, the present invention provides a method forcleaning a cleaning subject by allowing a liquid filled in a vessel tooverflow, wherein the cleaning subject is cleaned by pulling up thecleaning subject from the liquid filled in the vessel while allowing theliquid to overflow, or wherein the cleaning subject is cleaned bypulling up the cleaning subject from the liquid while increasing theflow rate of the overflowing liquid.

[0031] In accordance with another aspect of the present invention, thereis provided a cleaning apparatus of a cleaning subject comprising afirst vessel for containing a liquid, a flow rate control device forallowing the liquid to overflow from the vessel, a circulation devicefor feeding the overflow liquid to the vessel again, and a second vesselprovided between the first vessel and the liquid circulation device.

[0032] In accordance with a further aspect of the present invention,there is provided a method for cleaning the substrate by allowing aliquid filled in a vessel to overflow, wherein the substrate is cleanedby pulling up the substrate from the liquid filled in the vessel whileallowing the liquid to overflow from the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is an illustrative drawing showing one example of thecleaning apparatus used for cleaning the electrophotographicphotosensitive member according to the present invention.

[0034]FIG. 2 is a schematic cross section of the film depositionapparatus for depositing a film on a cylindrical substrate by a RFplasma CVD method.

[0035]FIG. 3A is a schematic cross section of the film depositionapparatus for depositing a film on a cylindrical substrate by amicrowave plasma CVD method.

[0036]FIG. 3B is a cross section along the line X-X in FIG. 3A.

[0037]FIG. 4 is a schematic cross section of the film depositionapparatus for depositing a film on a cylindrical substrate by a VHFplasma CVD method.

[0038]FIGS. 5A or 5B are cross sections showing a layer construction ofthe electrophotographic photosensitive member.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0039] A method for cleaning a cleaning subject, especially the methodfor cleaning the electrophotographic photosensitive member, will bedescribed in the embodiment of the present invention in which analuminum substrate is used as an example.

[0040] The cause of the appearance of abnormal growth portions on thealuminum substrate is mainly divided as:

[0041] (A) solutes in the cleaning water used in the cleaning step ofdusts on the substrate and in the drying step are adhered to serve asnuclei; and

[0042] (B) surface defects on the substrate serve as nuclei.

[0043] It was made possible to prevent adhesion of dusts and solutes asdescribed in (A) to some degree by attempting to make the cutting andwashing workshop of the substrate clean and strictly cleaning inside ofthe furnace, along with cleaning the surface of the substrateimmediately before depositing a film. The causes were solved by washingthe substrate with halogenated solvents such as trichloroethane.However, a cleaning method using water should be considered in place ofcleaning with chlorinated solvents, because use of these chlorinatedsolvents has been restricted in recent years for preventing pollutionsuch as destruction of the ozone layer.

[0044] A method for cleaning aluminum containing specified componentswith a specified cleaning method should be considered, in order toreduce surface defects as described in (B).

[0045] Aluminum containing silicon is preferably used as a conductivesubstrate in the present invention. While it is usually preferable thatthe content of impurities in aluminum is smaller, oxides are liable togrow when quite pure aluminum is fused for processing into a shape ofthe substrate, generating many abnormal growth portions. Formation ofoxides can be suppressed by adding Si atoms in aluminum to be processedby fusion.

[0046] It is preferable in the present invention to use an aqueouscleaning solvent, in which silicate salts are dissolved in water ascorrosion preventive agents (inhibitors), for cleaning the substrate.The aqueous cleaning solvent containing an inhibitor is used forprevention of corrosion, because aluminum containing silicon (Si) atomsmay be corroded with water mainly at the portions where Si atoms arelocally concentrated. Although corrosion may occur at the portionswhere, not only Si atoms, other atoms such as Fe atoms or Cu atoms arelocally concentrated, corrosion of the aluminum substrate containingthese atoms during cleaning can be efficiently prevented by using aninhibitor such as a silicate salt. Since corrosion becomes evident whenthe temperature of the cleaning water is high or when the cleaning watercontains magnesium together with Si, Fe and Cu in order to improvecutting susceptibility, the substrate is preferably washed with anaqueous cleaning solvent containing the corrosion preventive agent.

[0047] An Al—Si—O coating film is formed by the inhibitor on the surfaceof the aluminum, which is thought to prevent corrosion of the aluminumsubstrate. Once the Al—Si—O coating film has been formed, no defectsremain on the surface of the substrate, thereby allowing abnormal growthof films accompanied by deposition of a film as a functional film to beprevented.

[0048] In other words, generation of abnormal growth can be prevented bywashing aluminum with an aqueous cleaning solution containing a silicatesalt as an inhibitor, consequently improving characteristics of theelectrophotograph formed.

[0049] The steps for cleaning the surface of the substrate preferablycomprise three steps of degreasing, rinsing and drying in the presentinvention. The circulation volume of the cleaning solvent when thesubstrate is pulled up from the vessel, or when the substrate travelsupward in the solvent filled in the vessel, is increased relative to thecirculation volume, or the solvent overflows the vessel, when thesubstrate is dipped in the solvent in at least one step described above.Consequently, contaminants, such as oil components floating on theliquid surface or in the liquid by being degreased from the surface ofthe substrate when the substrate is dipped in the solvent, are preventedfrom adhering again on the surface of the substrate when the substrateis pulled up from the vessel. The effect for preventing contaminantsfrom adhering again can be further enhanced by showering, if required,the cleaning solvent on the surface of the substrate that has beenpulled up from the liquid in at least one step of the three steps.

[0050] An amorphous silicon film is preferably deposited on thesubstrate by the plasma CVD method in the present invention. The plasmaCVD method can be divided into three processes of decomposing thematerial gas in the gas phase, transferring active species from thedischarge space to the surface of the substrate, and allowing the activegas species to react on the surface of the substrate. The surfacereaction process among the three processes plays an important role indetermining the structure of the completed deposition film. Althoughdeposition of a film in the surface reaction process is largely affectedby the temperature, material and the shape of the surface of thesubstrate, and adsorbed substances on the surface of the substrate, theeffect of the absorbed substances is the largest among them.

[0051] A high purity aluminum substrate may absorb water on its surface.When an amorphous silicon film comprising silicon, or an amorphoussilicon film comprising silicon containing hydrogen and fluorine, isdeposited on the substrate by the plasma CVD method, for example, in theconventional art, compositions and structures at the interfaces betweenthe substrate and deposition film may be locally varied due to waterabsorbed on the surface of the substrate. When the substrate on thesurface of which films containing abnormal growth portions are depositedis used for the electrophotographic process as the electrophotographicphotosensitive member, differences in charge injection ability orsurface potential may be caused between the portions as described aboveand the other portions on the surface of the substrate, consequentlycausing irregularity of image qualities of the image obtained by theelectrophotographic process. An Al—Si—O coating film is formed using asilicate salt as an inhibitor on the surface of the substrate in thepresent invention, prior to forming a functional film comprisingamorphous silicon by the plasma CVD method. This is because an interfacecapable of favorably exchanging electric charges with the substrate isformed to enable good quality of the deposition film to be formed,thereby making it possible to improve electrification ability of thesubstrate as well as such electrophotographic characteristics as lightsensitivity.

[0052] The embodiment of the present invention will be describedhereinafter in more detail with reference to FIGS. 1, 2, 3, 4 and 5. Theterm “760 Torr” as used herein refers to 1 atm, or 101.325 kPa.

[0053] The substrate is treated by the steps comprising degreasing thesurface of the substrate and the substrate itself, rinsing the surfaceof the substrate, and drying the surface of the substrate in this orderin the present embodiment, prior to depositing a film on the substrate.The rinsing step is divided into two steps of the rinsing step 1 andrinsing step 2, wherein in the rising step 1 coating film is formed onthe substrate after completing the degreasing step using a cleaningsolution in which a silicate salt is dissolved, and the substrate aftercompleting the rinsing step 1 is rinsed again in the rinsing step 2, inorder to enhance the rinsing effect. Also, fats and oils, and residuessuch as halogenated substances, are efficiently removed by increasingthe circulation volume of the cleaning solvent when the substrate ispulled up, relative to the circulation volume when the substrate isdipped in the cleaning solvent, in at least one step including thedegreasing step according to the embodiment of the present invention. Acoating film having a corrosion preventive effect can be also formed onthe surface of the aluminum substrate, by allowing a silicate salt todissolve in water as a solvent to be used in the present invention.Consequently, an aluminum substrate provided with a high qualityamorphous deposition film can be obtained.

[0054]FIG. 1 denotes a schematic side view of the cleaning apparatus forcleaning the surface of the substrate according to the presentinvention. The cleaning apparatus comprises a treatment part 102 and asubstrate transfer mechanism 103. The treatment part 102 comprises asubstrate feed table 111, a degreasing vessel 121, a rinsing vessel-1131, a rinsing vessel-2 141, a drying vessel 151 and a substratetransfer table 171. Each vessel has a depth enough for placing theliquid surface above the substrate when a slender substrate is stoodstraight up in the vessel. The vessels are disposed with a distanceapart from one another. The solvent in each vessel is used for thatvessel only, and is not used for the other vessels. Temperature controldevices (not shown) are provided for the degreasing vessel 121, rinsingvessel-1 131, rinsing vessel-2 141 and drying vessel 151 for maintainingthe temperature of each vessel constant. The liquid filled in eachvessel may be used with a composition and temperature specified for thatvessel only depending on the purpose of the vessel. Ultrasonic vibrators(not shown) are provided for the degreasing vessel 121 and rinsingvessel 131 in order to enhance the degreasing effect and coating filmforming effect by preventing contaminants from adhering again. Nozzles181, 182 and 183, for showering the solvent on the substrate when it ispulled up from the vessel, are attached to the degreasing vessel 121,rinsing vessel-1 131 and rinsing vessel-2 141. The transfer mechanism103 comprises a transfer rail 165 and a transfer arm 161, a travelmechanism 162 travelling on the transfer rail 165, a chucking mechanism163 for holding the substrate 101, and an air cylinder 164 for allowingthe chucking mechanism 163 to move up and down.

[0055] Each of the degreasing vessel 121, rinsing vessel-1 131, rinsingvessel-2 141 and drying vessel 151 is composed of a vessel to serve as aliquid receiving space 197 for receiving the liquid, and a vessel toserve as a liquid collecting space 196 for collecting the overflowliquid. A circulation path for circulating the liquid to and collectingthe liquid from the receiving space is also provided in each vessel. Thecirculation path is composed of an overflow line 191, a reservoir 192and a circulation pump 193. The overflow liquid from each receivingspace when the flow rate for feeding the liquid to the vessel isincreased is pooled in the reservoir 192 via the overflow line 191 fromthe liquid collecting space at the top of each vessel 121, 131, 141 and151. The overflow line 191 is also connected to the bottom of the vesselto serve as the liquid collecting space 196. The liquid pooled in thereservoir 192 is fed to each vessel 121, 131, 141 and 151 again from thebottom parts by means of the circulation pump 193. The liquid feedvolume is controlled using a by-pass line 195 equipped with a valve as aflow rate control device, and particles such as debris are collected foreach vessel using a filter 194 prior to feeding the liquid to the vesselagain. When the circulation volume of the liquid is to be increased, theby-pass line 195 is closed or, when the circulation volume of the liquidis to be reduced, on the other hand, the by-pass line 195 is turnedopen. When the circulation volume is to be constant, opening of theby-pass line 195 is adjusted to a constant level. The composition of thecollected liquid to be fed to the vessel again can be also adjusted byproviding a composition adjustment device (not shown). The substrate 101can be pulled up from the liquid receiving space 197 without allowingthe oils and halogenated compounds to adhere again to the substrate 101while the overflow liquid is collected in the liquid collecting space196, because the liquid receiving space is provided so that the liquidlevel of the overflow liquid collected in the liquid collecting space196 always comes lower than the opening 198 of the liquid receivingspace 197. The liquid collecting space 196 is so configured as toenvelop the opening 198 of the liquid receiving space 197 from thebottom as shown in FIG. 1. Impurities such as oils and halogenatedcompounds collected in the liquid collecting space 196 together with theoverflow liquid from the liquid receiving space 197 can be collected atthe gas-liquid interface in the liquid collecting space. Theseimpurities can be readily collected and removed from the gas-liquidinterface. The impurities hardly enter into the circulation path sincethe overflow line 191 is provided at the bottom of the liquid receivingspace, enabling the overflow liquid to be effectively used again.

[0056] While the substrate to be used in this embodiment is a cylindermade of an aluminum alloy, a mirror cutting may be applied to thesubstrate before treating with the substrate cleaning apparatus. Themethod for mirror cutting comprises the steps of: setting a diamondblade (trade name: miracle bite, made by Tokyo Diamond Co.) to aprecision lathe equipped with an air-damper so as to secure an angularrake of five degree against the center angle of the cylinder; fixing thesubstrate with a vacuum chuck to the rotation flange of the lathe; andapplying mirror cutting with a peripheral speed of 1000 m/min and feedspeed of 0.01 mm/R to form a substrate with an outer diameter of 108 mmwhile spraying kerosine from an attached nozzle and simultaneouslyevacuating cutting debris through an evacuation nozzle.

[0057] The substrate after cutting is transferred to the cleaningapparatus. It is not always necessary to previously apply mirror cuttingas described above to the substrate to be used in the present invention.

[0058] The substrate is cleaned by the procedure as described below.

[0059] The substrate 101 placed on the substrate feed table 111 istransferred to the degreasing vessel 121 with the transfer mechanism 103to subject the substrate to the degreasing step. Water 122 prepared bydissolving a surfactant in pure water is filled in the degreasing vessel121, in which impurities such as dusts and oils adhered on the surfaceare washed off by separating them from the substrate 101 by ultrasonicwashing of the substrate 101. The substrate is held with the chuckingmechanism 163 and pulled up with the air cylinder 164 as an up-and-downmechanism. The circulation flow rate before pulling up the substrate isadjusted to be different from the flow rate after pulling up thesubstrate 101. While pulling up the substrate, an aqueous cleaningsolvent 122 after separating impurities such as oils that may adhere onthe substrate is showered from the nozzle 181 to the substrate 101.

[0060] The substrate 101 after completing the degreasing step istransferred to the rinsing vessel-1 131 with the transfer mechanism 103.Water kept at a temperature of 25° C. prepared by dissolving a silicatesalt is filled in the rinsing vessel-1 131, and a coating film is formedon the substrate in the vessel. Ultrasonic waves are also used, ifnecessary, in order to prevent impurities from adhering on thesubstrate. Water 123 is showered from the shower nozzle 182 to thesubstrate 101, if necessary, while pulling up the substrate 101 with theup-and-down mechanism 164.

[0061] The substrate 101 after completing the rinsing-1 step istransferred to the rinsing-2 vessel 141 for the next rinsing step bymeans of the transfer mechanism 103. Pure water 124 kept at atemperature of 25° C. is filled in the rinsing-2 vessel 141, where thesubstrate 101 is rinsed. Purity of pure water 124 is controlled in aconstant level with reference to an industrial conductivity meter (tradename: α 900R/C made by Horiba Seisakusho Co.). The substrate 101 ispulled up, if necessary, with the up-and-down mechanism 164, when purewater 124 is showered from the nozzle 183 to the substrate 101.

[0062] The substrate 101 after completing the rinsing-2 step is thentransferred to the drying vessel 151 by means of the transfer mechanism103 for the drying step. The drying vessel is filled with warmed purewater 125 kept at a temperature of 60° C. The substrate 101 dipped inwarmed pure water 125 is pulled up from the warm pure water and driedwhile being pulled up. Purity of the warmed pure water 125 is controlledto a given level with reference to the industrial conductivity meter(trade name: α 900R/C made by Horiba Seisakusho Co.).

[0063] The substrate 101 after completing the drying step is thentransferred to the transfer table 171 to carry the substrate from thecleaning apparatus.

[0064] A film deposition apparatus for forming a film on the surface ofthe substrate taken out of the system as shown in FIG. 1 will bedescribed hereinafter. FIG. 2 is a schematic drawing representing theside face of the film deposition apparatus using the plasma CVD method.A film mainly composed of amorphous silicon is deposited by using thefilm deposition apparatus in this embodiment.

[0065] With reference to FIG. 2, a reaction vessel 201 comprises a wall202 that serves as a base plate 204 and cathode electrode. A substrate206 is held by substrate holder 207 and also serving as an anodeelectrode, on which an amorphous silicon film is deposited, is placed atthe center of the cathode electrode 202. A top plate 203 is disposed oninsulator 205.

[0066] For depositing the amorphous silicon film on the substrate 206using the film deposition apparatus, a material gas inlet valve 211 isfirstly closed and an evacuation valve 214 is then turned open toevacuate the reaction vessel 201. The material gas inlet valve 211 isturned open when a vacuum gauge indicates 5×10⁻⁶ Torr. The gas travelsthrough a gas inlet tube 209 and flows into the reaction vessel 201. Thematerial gas flows from plural openings provided in the gas inlet tube209, which are denoted by dotted lines in FIG. 2 since it represents theside face of the openings. The gas flow rate is controlled to a givenlevel with a mass flow controller 212. For example, a material gas suchas SiH₄ is allowed to flow into the reaction vessel 201. Afterconfirming that the surface temperature of the substrate 206 is adjustedto a prescribed temperature with a heater 208, glow discharge isgenerated in the reaction vessel 201 by applying a desired electricpower to the high frequency power source 216 (at a frequency of 13.56MHz).

[0067] The substrate 206 is rotated with a motor (not shown) at aconstant speed using the longitudinal axis as a rotation axis duringdeposition, in order to uniformly deposit the film. The amorphoussilicon film is deposited on the substrate 206 as described above. Thereaction vessel 201 is evacuated by means of an exhaust pipe 213 andvacuum pump 215. Power is provided to the reaction vessel 201 by meansof power source 216.

[0068]FIG. 3A and FIG. 3B denotes the microwave plasma CVD apparatus (μwplasma CVD apparatus) 300 to be used in this embodiment. FIG. 3Arepresents a schematic side view while FIG. 3b represents a schematicplane view cut along the line X-X in FIG. 3A. The microwave plasma CVDapparatus 300 is composed of a reaction vessel 301 capable of evacuationforming, in the vacuum tight structure, and an evacuation device (notshown) for evacuating the reaction vessel. A microwave guide window 310formed with a material that efficiently transmits microwave electricpower into the reaction vessel and able to maintain vacuum tightness, amicrowave guide 311 connected to a microwave power source (not shown)via a stub tuner (not shown) and an isolator (not shown), a cylindricalsubstrate 306 on which films are deposited, a rotation mechanism 302 forrotating the cylindrical substrate 306, a substrate heater 303, and amaterial gas introduction tube 308 also serving as an electrode forapplying an outer electric bias for controlling plasma potential areinstalled in the reaction vessel 301. The material gas introduction tube308 is connected to a bias electric source 309, and the inside of thereaction vessel 301 is also connected to a diffusion pump (not shown)via the evacuation tube 304. The material gas is introduced into a spacesurrounded by the cylindrical substrate 306 via the material gasintroduction tube 308, forming a discharge space 407.

[0069] The film is deposited as follows with this apparatus based on themicrowave plasma CVD method (μw-PCVD method).

[0070] The cylindrical substrate 306 is attached in the reaction vessel301 and is rotated by means of a rotation device 302. The inside of thereaction vessel 301 is evacuated via the evacuation tube 304 to adjustthe pressure in the reaction vessel 301 to 1×10⁻⁶ Torr or less.Successively, the material gas to be heated is introduced into thereaction vessel 301 via the material gas introduction tube 308 to adesired inner pressure, and the cylindrical substrate 306 is heated.After completing preparation of deposition, a charge injection rejectlayer, a photosensitive layer and a surface layer are formed on thecylindrical substrate 306.

[0071] Opening of the main valve (not shown) is adjusted with referenceto the indication of a vacuum gauge (not shown) in order to adjust theinner pressure of the discharge space 407 to a prescribed pressure of133 Pa. After stabilizing the pressure, a microwave with a frequency of500 MHz or more, preferably 2.45 GHz, is generated with a microwavepower source (not shown). The microwave power source (not shown) isadjusted to a prescribed output power, and the microwave (μw) energy isintroduced to the discharge space 407 via the wave guide 311 andmicrowave guide window 310 to induce μw glow discharge. Simultaneously,an electric bias, for example a direct current bias, is applied to thegas inlet tube 308 that serves as an electrode from the power source309. The introduced material gas is dissociated by being excited withthe microwave energy in the discharge space 407 surrounded by thesubstrate 306. The cylindrical substrate 306 is rotated at a givenrotation speed by means of a rotation mechanism 302, in order touniformly deposit the layer.

[0072] After depositing a film with a prescribed thickness, the supplyof μw power is stopped and gas flow into the reaction vessel is closed,thus completing deposition of the film.

[0073] A desired multilayer structure is formed by repeating the similaroperations as described above.

[0074] The method for manufacturing an electrophotographic lightreceiving member formed by a high frequency plasma CVD (abbreviated asVHF-PCVD hereinafter) method using a VHF frequency band is describedwith reference to FIG. 4. The VHF-PCVD shown in FIG. 4 comprises areaction vessel 421 capable of evacuation and an evacuation device (notshown) for evacuating the reaction vessel. The inside of the reactionvessel 421 is equipped with a cylindrical substrate 426 on which a filmis deposited, a heater 423 for heating a supporting member, a materialgas introduction tube (not shown) and an electrode 425. A high frequencymatching box 428 is further provided at the electrode. The inside of thereaction vessel 421 is connected to a diffusion pump (not shown) via anevacuation tube 424. The space 427 surrounded by the cylindricalsubstrate 426 forms a discharge space.

[0075] The film is deposited by the VHF-PCVD method using this apparatusas follows.

[0076] The cylindrical substrate 426 is firstly attached in the reactionvessel 421 and is rotated with a driving device 422. The inside of thereaction vessel 421 is evacuated with an evacuation device (not shown)via the evacuation tube 424 to adjust the inner pressure of the reactionvessel 421 to 1×10⁻⁷ Torr or less. Then, the cylindrical substrate 426is heated at a temperature of 200 to 350° C. with the heater 423 forheating the supporting member.

[0077] After completing preparation of film deposition, each layer isformed on the cylindrical substrate 426 as follows. The material gas isintroduced into the discharge space 427 via the gas introduction tube(not shown) when the temperature of the cylindrical substrate 426 hasreached a prescribed temperature. Opening of the main valve (not shown)is adjusted referring the indication of a vacuum gauge (not shown) sothat the pressure in the reaction vessel 421 is stabilized at aprescribed pressure of 133 Pa or less.

[0078] When the pressure is stabilized, the VHF power source (not shown)at a frequency of 105 MHz is adjusted to a prescribed power, and the VHFpower is introduced into the discharge space 427 via the matching box428 to induce glow discharge. The introduced material gas is dissociatedby being excited with the discharge energy in the discharge space 427surrounded by the cylindrical substrate 426, and a film with aprescribed thickness is deposited on the cylindrical supporting member426, which is rotated at a desired rotation speed by means of a motor ofthe driving device 422 for rotating the supporting member in order touniformly deposit the film.

[0079] After depositing a film with a desired thickness, supply of theVHF power is stopped and the gas feed valve for the inlet gas to thereaction vessel is closed, thereby completing deposition of the film.

[0080] The desired light receiving multilayer is formed by repeatingsimilar operations as described above.

[0081] It is needless to say that the present invention is notrestricted by the embodiment as hitherto described. For example, thepull-up timing refers to a time when a part of the substrate dipped inwater 122 and 123, or pure water 124, or warm water 125 is exposed toout side of the liquid surface, besides the timing when the substratecompletely dipped in water 122 and 123, or pure water 124, or warm water125 is transferred upward.

[0082] The timing when a liquid such as water 122 and 123, or pure water124, or warm water 125 overflows refers to a time when substances suchas oils ready for being collected on the liquid surface have beencollected on the liquid surface. Oils collected on the liquid surfacemay be removed by overflow of the liquid, followed by halting andresuming overflow depending on requirements. Or, overflow may becontinuous. It is needless to say that the circulation flow rate ischanged when the overflow is continuous. In addition, circulation andoverflow allows insoluble substances that are liable to precipitate inthe liquid to be prevented from accumulating in the vessel, since theoverflow line 191 is connected to the bottom of a vessel to serve as aliquid receiving space 197.

[0083] A composition adjustment device (not shown) is provided in orderto eliminate impurities after collecting pure water used from the dryingstep through the rinsing-2 step. The composition of the collected liquidis adjusted to the substantially same component as the liquid used fromthe degreasing step through the rinsing-1 step, and the liquid may beused in the degreasing step.

[0084] The liquid should not necessarily flow through the circulationpath in the present invention, when the liquid overflows from the liquidreceiving space.

[0085] In other words, impurities are required merely to be efficientlyremoved to outside of the liquid receiving space. For attaining theeffect above, the liquid may be overflowed by directly feeding theliquid from a liquid feed device (not shown) to the liquid receivingspace.

[0086] Or, the flow rate of the overflow liquid from the liquidreceiving space may be increased by increasing the feed volume of theliquid fed from a feed device (not shown) to the liquid receiving space.

[0087] Or, the flow volume of the overflow liquid from the liquidreceiving space, or an apparent circulation flow volume, may beincreased by feeding the liquid from the liquid feed device to theliquid receiving space while the liquid is circulating through thecirculation path.

[0088] The liquid fed to the liquid receiving space from the liquid feeddevice (not shown) may be a fresh liquid, to consequently feed theliquid containing no impurities to the liquid receiving space and toreduce the relative concentration of impurities collected in the liquidreceiving space, thereby making it difficult for the impurities toadhere to the substrate again.

[0089] The substrate may be cleaned by pulling it up from the liquidwhile the liquid is overflowing, because the liquid surface sometimeslowered during travel of the substrate from in the liquid to outside ofthe liquid, even when the liquid is continuously fed to the vessel. Whenthe liquid level is lowered, it does not overflow the vessel andconsequently fails to remove the impurities to outside of the vessel.Accordingly, when the substrate is cleaned by pulling it up while theliquid is overflowing in the present invention, the impurities areprevented from adhering to the substrate again.

[0090] While the shower nozzle is used for either the degreasing step orthe rinsing step, the shower nozzle may be used for at least one step ofthe present invention. It is preferable to remove the impurities in thedegreasing step required to have high cleaning effect, by showering thesubstrate with the shower nozzle.

[0091] The shower nozzles are provided inside of each vessel so as toprevent the liquid sprayed to the substrate from scattering from thevessel to outside of the vessel. Accordingly, the vessels may bedisposed close to one another, or in adjoining relation with each other,to allow the overall cleaning apparatus to be small in size. The showernozzle may be provided outside of each vessel in the present invention,provided that the liquid can be substantially sprayed to the substrate.

[0092] The setting angle of the shower nozzles 181, 182 and 183 may bedesigned to be freely adjustable. For example, when the shower spray isdirected downward, the liquid fed from each shower nozzle can be readilyreceived by the vessel for each step, also preventing feed water fromscattering into the other vessel.

[0093] A substrate subjected to a mirror cutting for flattening therough surface of the substrate, or a substrate subjected to a non-mirrorcutting for preventing interference fringes from appearing, or asubstrate having desired concave and convex patterns may be used in thepresent invention.

[0094] Since corrosion is accelerated at the partially protrudedportions containing a high concentration of Si, Fe and Cu atoms on thealuminum surface, a silicate salt as an inhibitor for preventingabnormal growth is preferably added in the rinsing step in the presentinvention to form a coating film.

[0095] The inhibitor may be also dissolved in the liquid to be used forthe degreasing step, provided that a coating film forming treatment isapplied prior to exposing the substrate to pure water.

[0096] While examples of the inhibitors include a phosphate salt,silicate salt and borate salt, the silicate salt is especiallypreferable in the present invention.

[0097] While the preferable silicate salt includes potassium silicateand sodium silicate, potassium silicate is especially preferable in thepresent invention.

[0098] The possible surfactants to be used in the present inventioninclude an anionic surfactant, a cationic surfactant, a nonionicsurfactant, an amphoteric surfactant, or a mixture thereof. Use of acarboxylic acid salt, sulfonic acid salt, sulfuric acid salt andphosphate ester salt of an anionic surfactant, or a fatty acid ester ofa nonionic surfactant is preferable in the present invention.

[0099] Pure water, as a solvent for dissolving a surfactant or aninhibitor or as pure water itself, used in the degreasing step, rinsingstep or drying step according to the present invention is desirably asemiconductor grade pure water, especially a super LSI grade ultra-purewater. Actually, the grade indicating a resistivity at a watertemperature of 25° C. of 1 MΩ·cm or more as a lower limit, preferably 3MΩ·cm or more, and 5 MΩ·cm or more as an optimum is suitable for thepresent invention. While any level up to a theoretical resistivity(18.25 MΩ·cm) is possible for the upper limit, a resistivity of 17 MΩ·cmor less, preferably 15 MΩ·cm and most suitably 13 MΩ·cm is appropriatein the present invention considering the production cost andproductivity. A concentration of fine particles with a particle size of0.2 μm or less of 10,000/ml or less, preferably 1,000/ml or less andmost suitably 200/ml is suitable in the present invention. Concentrationof microorganisms as total viral microorganisms of 100 cells/ml or less,preferably 10 cells/ml and most suitably one cell/ml or less isappropriate in the present invention. Concentration of organicsubstances (TOC) of 10 mg/liter or less, preferably 1 mg/liter or lessand most suitably 0.2 mg/liter or less is appropriate in the presentinvention. Of course, the aqueous solution in which solutes aredissolved or pure water filled in the vessel after being used forcleaning are not always required to maintain such purity grade asdescribed above.

[0100] While an activated charcoal method, a distillation method, anion-exchange method, a filtration method, a reverse osmosis method and aUV sterilization method are known in the art for obtaining water with aquality as described above, it is desirable to improve the water qualityto a required level by combining some of these methods.

[0101] When the temperature of water containing the surfactant to beused in the degreasing step is too high, liquid spots appear on thesurface of the substrate, where the deposition film is liable to bepeeled. When the temperature is too low, on the other hand, thedegreasing effect and film forming effect become so small that asufficient coating film cannot be obtained. Consequently, a temperaturerange of 10° C. or more and 60° C. or less, preferably 15° C. or moreand 50° C. or less, and most suitably 20° C. or more and 40° C. or lessis appropriate in the present invention.

[0102] When an ultrasonic wave is used in the degreasing step accordingto the present invention, the effective frequency range of theultrasonic wave used is preferably 100 Hz or more and 10 MHz or less,more preferably 1 MHz or more and 5 MHz or less, and most suitably 10kHz or more and 100 kHz or less. The effective output power range of theultrasonic wave used is preferably 0.1 W/liter or more and 1 kW/liter orless, and more preferably 1 W/liter or more and 100 W/liter or less.

[0103] When the concentration of the aqueous cleaning solvent containinga surfactant to be used in the degreasing step according to the presentinvention is too high, solvent spots remain on the substrate afterpulling up the substrate, causing peeling of the deposition film.

[0104] Accordingly, a concentration range of the surfactant contained ina unit volume of water of 0.1 wt % or more and 20 wt % or less,preferably 1 wt % or more and 10 wt % or less; and most suitably 2 wt %or more and 8 wt % or less is appropriate in the present invention.

[0105] When the pH of water containing the surfactant is too high,solvent spots remain on the substrate, causing peeling of the depositionfilm.

[0106] Accordingly, a pH value of water containing the surfactant of 8or more and 12.5 or less, preferably 9 or more and 12 or less, and mostsuitably 10 or more and 11.5 or less is suitable in the presentinvention.

[0107] While the circulation flow rate (the first circulation flow rate)Q₁ when the substrate is dipped and the circulation flow rate (thesecond circulation flow rate) Q₂ when the substrate is pulled up arechanged in the present invention, the circulation flow rate may bechanged in any step. While it is most suitable to change the circulationflow rate at the degreasing step, the ratio between Q₁ and Q₂ satisfiesthe relation of 0.1≦Q₁/Q₂≦0.8, preferably 0.2≦Q₁/Q₂≦0.7, and morepreferably 0.3≦Q₁/Q₂≦0.6.

[0108] When the concentration of the silicate salt contained in unitvolume of water is too high in the present invention, solvent spotsremain on the substrate, causing peeling of the deposition film. Whenthe concentration is too low, on the other hand, the effect of thecoating film is reduced and fails to obtain the effect of the presentinvention. Accordingly, a concentration of 0.5 wt % or more and 2 wt %or less, preferably 0.1 wt % or more and 1.5 wt % or less, and mostsuitably 0.2 wt % or more and 1 wt % or less is appropriate in thepresent invention.

[0109] When the pH of water containing the silicate salt is too high inthe present invention, solvent spots remain on the substrate, causingpeeling of the deposition film. When the pH value is too low, on theother hand, the effect of the coating film is reduced to and fails tosufficiently obtain the effect of the present invention. Accordingly,the pH value of water containing the silicate salt of 8 or more and 12.5or less, preferably 9 or more and 12 or less, and most suitably 10 ormore and 11.5 or less is appropriate in the present invention.

[0110] In the present invention, too thin of a film thickness of thecoating film formed on the aluminum substrate fails to exhibit itseffect, but too large of a film thickness reduces conductivity betweenthe film and the aluminum substrate, causing an adverse effect.Accordingly, a coating film thickness of 5 Å or more and 150 Å or less,preferably 10 Å or more and 130 Å or less, and most suitably 15 Å ormore and 120 Å or less is appropriate in the present invention.

[0111] When the proportion of Si and O is small in the composition ratioof the Al—Si—O coating film (a coating film of the silicate salt), thecoating film is not sufficient since the proportion of Al becomes large.However, a larger proportion is also not appropriate since conductivityis decreased. An appropriate ratio of Si is 0.1 or more and 0.5 or less,preferably 0.15 or more and 0.4 or less, and most suitably 0.2 or moreand 0.35 or less, when the proportion of Al is taken as unity. Anappropriate ratio of oxygen (O) is 1 or more and 5 or less, preferably1.5 or more and 4 or less, and most suitably 2 or more and 3 or less,when the proportion of Al is taken as unity.

[0112] Showering the surface of the substrate after forming the coatingfilm is also effective in the present invention.

[0113] Using the ultrasonic wave is effective for the present invention.The effective frequency of the ultrasonic wave is preferably 100 Hz ormore and 10 MHz or less, more preferably 1 kHz or more and 5 MHz orless, and most suitably 10 kHz or more and 100 kHz or less. Theeffective output power of the ultrasonic wave is 0.1 W/liter or more and1 kW/liter or less, and more preferably 1 W/liter or more and 100W/liter or less.

[0114] The rinsing effect or drying effect may be improved in thepresent invention by dissolving carbon dioxide in the solvent to be usedin the rinsing step or drying step. Quality of the water is veryimportant, and pure water of the semiconductor grade, especiallyultra-pure water of the super LSI grade before dissolving carbon dioxideis desirable. Practically, water suitable in the present invention has alower limit of conductivity of 10 MΩ·cm or more, preferable conductivityof 3 MΩ·cm or more, and most suitable conductivity of 5 MΩ·cm or more at25° C. Although an upper limit of up to a theoretical conductivity(18.25 MΩ·cm) is possible, a conductivity of 17 MΩ·cm or less,preferably 15 MΩ·cm or less, and most suitably 13 MΩ·cm or less isappropriate in the present invention. A particle concentration of fineparticles with a particle size of 0.2 μm or less of 10,000/1 ml or less,preferably 1,000/ml or less and most suitably 200/ml is suitable in thepresent invention. Concentration of microorganisms as total viralmicroorganisms of 100 cells/ml or less, preferably 10 cells/ml and mostsuitably 1 cell/ml or less is appropriate in the present invention.Concentration of organic substances (TOC) of 10 mg/liter or less,preferably 1 mg/liter or less and most suitably 0.2 mg/liter or less isappropriate in the present invention. Of course, the aqueous solution inwhich carbon dioxide is dissolved is not always required to maintainsuch purity grade as described above. Or, the quality of water to beused for rinsing or drying the substrate is not always required tosatisfy such purity grade as described above.

[0115] While an activated charcoal method, a distillation method, anion-exchange method, a filtration method, a reverse osmosis method and aUV sterilization method are known in the art for obtaining water with aquality as described above, it is desirable to improve the water qualityto a required level by combining some of these methods.

[0116] While the possible concentration of carbon dioxide dissolved inthe solvent is up to its saturation concentration, bubbles are liable tobe generated by fluctuation of water temperature when the concentrationis too high, causing solvent spots by adhering the bubble on the surfaceof the substrate. Further, the substrate may be damaged when theconcentration of dissolved carbon dioxide is too large because the pH ofthe solution is lowered. However, the effect of the present inventioncannot be attained when the concentration of dissolved carbon dioxide istoo low.

[0117] Accordingly, the concentration of carbon dioxide should beoptimized by taking the required quality of the substrate intoconsideration.

[0118] Preferable concentration of carbon dioxide according to thepresent invention is usually 60% or less, more preferably 40% or less,of the saturation concentration.

[0119] Practically, the concentration of carbon dioxide in the solventto be used in the rinsing step according to the present invention iscontrolled by conductivity or pH of water. The effect of the presentinvention becomes evident when water has a controlled conductivity inthe range of preferably 2 μS/cm or more and 40 μS/cm or less, morepreferably 4 μS/cm or more and 30 μS/cm or less, and most preferably 6μS/cm or more and 25 μS/cm or less; and when water has a controlled pHvalue in the range of 3.8 or more and 6 or less, and more preferably 4.0or more and 5.0 or less. Conductivity is measured with a conductivitymeter by correcting the measured value to the value at 25° C.

[0120] The appropriate water temperate in the present invention is inthe range of 5° C. or more and 90° C. or less, preferably 10° C. or moreand 55° C. or less, and most suitably 15° C. or more and 40° C. or less.

[0121] Carbon dioxide is dissolved in water by any method, including amethod by bubbling and a method using a parting membrane. Using water inwhich carbon dioxide is dissolved can prevent the effect of cations suchas sodium ions probable by using carbonate salts such as sodiumcarbonate for obtaining carbonate ions.

[0122] When the surface of the substrate is washed with water obtainedby dissolving carbon dioxide, the substrate is basically dipped in awater bath filled with water in which carbon dioxide is dissolved.However, the present invention is more effected by simultaneouslyapplying a stream, or bubbling by blowing air in water.

[0123] The suitable cleaning treatment time with water in which carbondioxide is dissolved is 10 seconds or more and 20 minutes or less,preferably 20 seconds or more and 20 minutes or less, and most suitably30 seconds or more and 10 minutes or less, in the present invention.

[0124] Practically, the concentration of carbon dioxide in the solventto be used in the drying step according to the present invention iscontrolled by the conductivity or pH of water. The effect of the presentinvention becomes evident when water has a controlled conductivity inthe range of preferably 5 μS/cm or more and 40 μS/cm or less, morepreferably 6 μS/cm or more and 35 μS/cm or less, and most preferably 8μS/cm or more and 30 μS/cm or less; and when water has a controlled pHvalue in the range of preferably 3.8 or more and 6.0 or less, and morepreferably 4.0 or more and 5.0 or less. Conductivity is measured with aconductivity meter by correcting the measured value to the value at 25°C. Purity of water in which carbon dioxide is dissolved, and the methodfor dissolving carbon dioxide in water may be the same as used in therinsing step.

[0125] The appropriate water temperate in the present invention is inthe range of 30° C. or more and 90° C. or less, preferably 35° C. ormore and 80° C. or less, and most suitably 40° C. or more and 70° C. orless.

[0126] The pull up velocity for drying by pull-up is very important.Appropriate velocity in the present invention is preferably 100 mm/minor more and 2000 mm/min or less, more preferably 200 mm/min, and mostsuitably 300 mm/min or more and 1000 mm/min or less.

[0127] Too long of a time interval between the cleaning treatment withcarbon dioxide water or pure water and introduction into the filmdeposition apparatus reduces the effect of the present invention, whiletoo short of a time interval makes the production step unstable.Therefore, the appropriate time interval in the present invention is 1minute or more and 8 hours or less, preferably 2 minutes or more and 4hours or less, and most suitably 3 minutes or more and 2 hours or less.

[0128] While it is preferable with respect to machinability andproduction cost as well as for obtaining good characteristics of thefilm that the substrate material is principally based on aluminum, thealuminum based material containing 10 ppm or more of iron (Fe), 10 ppmor more of silicon (Si) and 10 ppm or more of copper (Cu), with a totalcontent of Fe, Si and Cu relative to aluminum of more than 0.01 wt % andless than 1 wt % or less, is suitable in the present invention.

[0129] Allowing the substrate to contain magnesium is effective forimproving machinability of the substrate in the present invention. Themagnesium content is preferably in the range of 0.1 wt % or more and 10wt % or less, and more preferably 0.2 wt % or more and 5 wt % or less.

[0130] Other elements represented by the following element symbols suchas H, Li, Na, K, Be, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ag, Zn, Cd, Hg, B, Ca,In, C, Si, Ge, Sn, N, P, As, O, S, Se, F, Cl, Br and I may be containedin aluminum in the present invention other than Fe, Si and Cu.

[0131] While the shape of the substrate is determined depending onrequirements, an endless belt or a cylinder is most suitable for thepresent invention when the substrate is used for electrophotography suchas a continuous high speed copy machine. Although dimensions of thecylindrical substrate are not especially limited, a substrate having anouter diameter of 20 mm or more and 500 mm or less, and a length of 10mm or more and 1000 mm or less is practically preferable. While thethickness of the supporting member is appropriately determined so that adesired photoconductive member is formed, it may be as thin as possiblewithin a range sufficiently exhibiting the function as the supportingmember when the photoconductive member is required to be as thin aspossible. However, the thickness is usually 10 μm or more consideringproduction performance and easy handling as well as mechanical strength.

[0132] While the possible photosensitive substances to be used in thepresent invention include inorganic photosensitive substances such asamorphous silicon, selenium and cadmium sulfide, and organicphotosensitive substances, the effect is evident in a non-crystallinephotosensitive substance containing silicon such as amorphous silicon.

[0133] Examples of the material gases to be used in depositing a filmfor producing a non-crystalline photosensitive substance containingsilicon include material gases for forming amorphous silicon such assilane (SiH₄), disilane (Si₂H₆), tetrafluorosilicon (SiF₄) andhexafluorosilicon (Si₂F₆), or a mixed gas thereof.

[0134] Examples of dilution gases include hydrogen (H₂), argon (Ar) andhelium (He).

[0135] Examples of characteristics improving gases for arbitrarilycontrolling band gap width of the deposition film include compoundscontaining nitrogen such as nitrogen (N₂ and ammonia (NH₃); compoundscontaining oxygen such as oxygen (O₂), nitric oxide (NO), nitrogendioxide (NO₂), nitrous oxide (N₂O), carbon monoxide (CO) and carbondioxide (CO₂); hydrocarbons such as methane (CH₄), ethane (C₂H₆)ethylene (C₂H₄) , acetylene (C₂H₂) and propane (C₃H₈); and fluorinatedcompounds such as germanium tetrafluoride (GeF₄) and nitrogen fluoride(NF₃); and a mixed gas thereof.

[0136] Simultaneously introducing a dopant gas such as diborane (B₂H₆),boron fluoride (BF₃) and phosphine (PH₃) for doping in the dischargespace is also effective in the present invention.

[0137] Any total thickness of the deposition film deposited on thesubstrate is acceptable in the electrophotographic photosensitive memberaccording to the present invention, especially good images as theelectrophotographic photosensitive member can be obtained at a thicknessof 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70μm or less, and most suitably 15 μm or more and 50 μm or less.

[0138] While the effect of the present invention was evident in anyrange of the pressure in the discharge space during deposition of thefilm, especially good results in stability of discharge and uniformityof deposition films were obtained with good repeatability when thepressure was 66.5×10⁻³ Pa or more and 13.3 Pa or less, preferably13.3×10⁻¹ Pa or more and 6.65 Pa or less.

[0139] While the effective temperature of the substrate duringdeposition of the film is in the range of 100° C. or more and 500° C. orless, remarkable effects were confirmed at a temperature of 150° C. ormore and 450° C. or less, preferably 200° C. or more and 400° C. orless, and most suitably 250° C. or more and 350° C. or less.

[0140] A heating element with a vacuum specification may be used forheating the substrate in the present invention. Examples of them includeelectric resistance heating elements such as a sheathed coil heater, aplate heater and a ceramic heater; radiation heating elements such as ahalogen lamp and an infrared lamp; and heat exchange heating elementsusing liquids and gases as heating media. Metals such as stainlesssteel, nickel, aluminum and copper, ceramics and heat-resistant polymerresins may be used for the surface material of the heating device.Otherwise, a vessel exclusively used for heating may be provided besidesthe reaction vessel, in order to transfer the substrate into thereaction vessel in vacuum after heating the substrate. The heatingdevices as described above may be used alone or in combination thereof.

[0141] Either a DC current, an RF current, a microwave or a wave in theVHF band may be used for the energy for generating a plasma. However,the effect of the present invention is effected by using a microwave forthe energy for generating a plasma, because abnormal growth due tosurface defects evidently appears, the microwave is absorbed by theabsorbed moisture, and surface changes become more evident.

[0142] Although the microwave electric power for generating a plasma bymicrowave may have an intensity enough for discharge, the electric powerappropriate for the present invention is 100 W or more and 10 kW orless, preferably 500 W or more and 4 KW or less.

[0143] It is effective in the present invention to apply a voltage (abias voltage), preferably at least along the direction where cationsimpinge on the substrate, in the discharge space while depositing afilm. It is also desirable to apply a bias voltage containing a DCcomponent of 1 V or more and 500 V or less, preferably 5 V or more and100 V or less, while depositing a film.

[0144] When the microwave is guided into the reaction vessel through awindow made of a dielectrics, a material that causes small loss of themicrowave such as alumina (Al₂O₃), aluminum nitride (AlN), boron nitride(BN), silicon nitride (SiN), silicone oxide (SiO₂), beryllium oxide(BeO), Teflon and polystyrene is used for the dielectrics for thewindow.

[0145] In the method for depositing a film in which the discharge spaceis surrounded by plural substrates, the substrates are preferablydisposed with a distance of 1 mm or more and 50 mm or less. While thenumber of the substrates is determined considering productivity so as tobe able to constitute the discharge space, three or more, preferablyfour or more substrates are appropriately used.

[0146] Although the present invention can be applied for any method formanufacturing the electrophotographic photosensitive member, it isespecially effective to dispose the substrates so as to surround thedischarge space to deposit a film by introducing the microwave from atleast one terminal side of the substrate.

[0147] The photoelectric photosensitive member manufactured by themethod according to the present invention is widely used in anelectrophotographic copy machine as well as in various applicationfields of electrophotography such as a laser beam printer, CRT printer,LED printer, liquid crystal printer and laser scanning printing machine.

EXAMPLES

[0148] The present invention will now be described by way of examples ofthe method for cleaning the substrate for the electrophotographicphotosensitive member. Since the present invention is effective for anyobjects that are cleaned by dipping in a cleaning solution, theinvention is not limited to these examples.

Example 1

[0149] The surface of a cylindrical substrate, made of aluminumcontaining 0.05 wt % of Si, 0.03 wt % of Fe and 0.01 wt % of Cu, with adiameter of 108 mm, a length of 385 mm and a wall thickness of 5 mm wasmachined by the same method as described in the foregoing method formanufacturing the electrophotographic photosensitive member according tothe present invention. The composition ratio of all the elementsexisting on the substrate shown in the present invention was measuredusing a X-ray fluorescence analyzer comprising magnesium (Mg) as ananode under the conditions of 15 kV and 400 W, or an energy resolutionof 0.98 ev (Ag3d5/2) in a vacuum of 1×10⁻⁹ Torr or less.

[0150] Fifteen minutes after completing the cutting step, the substratewas transferred to the cleaning apparatus of the present invention shownin FIG. 1. The substrate was treated in the degreasing step with asurfactant (a nonionic surfactant), rinsing step-1 and rinsing step-2,and drying step under the conditions as shown in TABLE 1. Thecirculation volume of water 122 in the degreasing step was different inthe pull-up process from other processes of the substrate as shown inTABLE 3. After completing the treatments in the cleaning apparatus,surface appearance and presence of stains by liquid traces on thesurface were visually inspected. The results are also listed in TABLE 3.The concentration of the surfactant in water used for the degreasingstep was 3 wt %. The silicate salt used as an inhibitor in the rinsingstep-1 of this example was potassium silicate with a concentration of0.3 wt % in water.

[0151] Then, an amorphous silicon film was deposited on thesurface-treated substrate under the conditions shown in TABLE 2 usingthe film deposition apparatus to manufacture a rejection typeelectrophotographic photosensitive member as shown in FIG. 5A. Thereference numerals 501, 502, 503 and 504 denote an aluminum substrate, acharge injection reject layer, a photoconductive layer and a surfacelayer, respectively, formed in this order.

[0152] Electrophotographic characteristics of the electrophotographicphotosensitive member manufactured were evaluated as follows. Theprocess speed of the electrophotographic photosensitive membermanufactured was changed in a range of 200 to 800 mm/sec in theexperiment. A latent image was formed on the surface of theelectrophotographic photosensitive member, subjected to coronaelectrification from a charging device at an applied voltage of 6 to 7kv, exposure to a laser beam with a wavelength of 788 nm. Thephotosensitive member was placed in a copy machine (NP 6650 made byCanon Co.), reformed so as to be able to print the image on a transferpaper by a conventional copying process, and the presence of blackspots, image defects and electrophotographic characteristics, andenvironmental adaptability were totally evaluated based on theevaluation criteria as will be described hereinafter. The results arelisted in TABLE 3.

[0153] Stains on the substrate observable with the naked eyes wereconfirmed by allowing a strong exposure light to reflect on the surfaceof the substrate after cleaning. Symbols representing the evaluationresults are as follows:

[0154] {circle over (∘)}: very good;

[0155] ◯: no stains, good;

[0156] Δ: pale stains, no practical problems; and

[0157] x: evident stains.

[0158] Image samples in which image defects appear most frequently amongthe test images, obtained by copying totally half-tone printing mattersand typescripts while changing the process speed, were selected forevaluation. The evaluation method comprises observing over the imagesample with a magnification glass to count the number of white dots in aunit area. The evaluation results are represented in the table using thefollowing four marks:

[0159] {circle over (∘)}: very good;

[0160] ◯: good, very fine defects are locally observed, but there are noproblems;

[0161] Δ: very fine defects are observed on the overall surface, butthere are no practical problems; and

[0162] x: large defects are observed on the overall surface withpractical problems.

Comparative Example 1

[0163] The substrate was cleaned by the same method as described inExample 1, except that the circulation volume in the degreasing step wasnot charged. A rejection type electrophotographic photosensitive memberwas manufactured and evaluated by the same method as in Example 1. Theresults are listed in TABLE 3, TABLE 4 and TABLE 6 as comparativeexamples. TABLE 1 TREATING DEGREASING RINSE-1 RINSE-2 DRYING CONDITIONSLIQUID IN THE PURE WATER PURE WATER PURE WATER PURE VESSEL CONTAINING(10 MΩ · CM) (10 MΩ · CM) WATER NONIONIC (10 MΩ · CM) DETERGENT LIQUID40° C. 25° C. 25° C. 45° C. TEMPERATURE TREATMENT TIME 5 MINUTES 1.5MINUTES 1 MINUTE 1 MINUTE OTHER CONDITIONS · ULTRASONIC — — —  TREATMENT·FLOW RATE Q₁  DURING DIPPING  ARE DIFFERENT  FROM FLOW RATE  Q₂ DURING PULL-UP INHIBITOR — — — —

[0164] TABLE 2 CHARGE INJECTION REJECT PHOTOCODUCTIVE LAYER LAYERSURFACE LAYER  4 400 400→430→430 186→169→30→25 800 800→1250→1250 15001.25 6.5 — 104 3.7 3.7→7.3→7.3 4.0→5.98 POWER (W) 160 320→700→700 250TIME (MIN) 34 INITIAL 10 + 350  31

[0165] TABLE 3 FLOW RATE RATIO APPEARANCE RESULTS OF IMAGE (Q₁/Q₂)(SOLVENT STAIN) EVALUATION  0.05 Δ Δ 0.1 ◯ ◯ 0.2 ◯ ◯ 0.3 ⊚ ⊚ 0.4 ⊚ ⊚ 0.5⊚ ⊚ 0.6 ⊚ ⊚ 0.7 ◯ ◯ 0.8 ◯ ◯ 1.0 Δ Δ 1.1 Δ Δ COMPARATIVE Δ Δ EXAMPLE 1

Example 3

[0166] A rejection type electrophotographic photosensitive member wasmanufactured and evaluated by the same method as in Example 1, exceptthat the same substrate was used and the substrate was pulled up byshowering the solution having the same composition as used in thedegreasing step. The results of evaluations are shown in TABLE 4. Thesolution filled in the degreasing vessel was collected and used forshowering after separating oils from water using a oil/water separator(not shown). The results in Comparative Example 1 are also described inTABLE 4 together with the results in EXAMPLE 1. TABLE 4 FLOW RATE RATIOAPPEARANCE RESULTS OF IMAGE (Q₁/Q₂) (SOLVENT STAIN) EVALUATION  0.05 Δ Δ0.1 ◯ ◯ 0.2 ⊚ ⊚ 0.3 ⊚ ⊚ 0.4 ⊚ ⊚ 0.5 ⊚ ⊚ 0.6 ⊚ ⊚ 0.7 ⊚ ⊚ 0.8 ◯ ◯ 1.0 Δ Δ1.1 Δ Δ COMPARATIVE Δ Δ EXAMPLE 1

[0167] As is evident from TABLE 4, evaluations of the image includingappearance and presence of stains are improved by showering the cleaningsolution to the substrate during pulling-up of the substrate even whenthe circulation volume ratio is increased or decreased relative to thatin Example 2.

Example 3

[0168] A rejection type electrophotographic photosensitive member shownin Example 1 was manufactured, after cleaning the substrate by the samemethod as in Example 2, except that the circulation volume of thecleaning solution was changed in the vessels other than the degreasingvessel by the same method as in Example 2 as shown in TABLE 5. TABLE 5TREATING DEGREASING RINSE-1 RINSE-2 DRYING CONDITIONS LIQUID IN THE PUREWATER PURE WATER PURE WATER PURE WATER VESSEL CONTAINING (10 MΩ · CM)(10 MΩ · CM) (10 MΩ · CM) NONIONIC DETERGENT LIQUID 40° C. 25° C. 25° C.45° C. TEMPERATURE TREATMENT TIME 5 MINUTES 1.5 MINUTES 1 MINUTE 1MINUTE OTHER CONDITIONS ·ULTRASONIC ·SHOWER OF ·SHOWER OF  ·SHOWER OF TREATMENT  SOLUTION  SOLUTION  SOLUTION ·SHOWER OF ·FLOW RATE Q₁ ·FLOWRATE Q₁ ·FLOW RATE Q₁  SOLUTION  DURING  DURING  DURING ·FLOW RATE Q₁ DIPPING IS  DIPPING IS  DIPPING IS  DURING DIPPING  DIFFERENT DIFFERENT  DIFFERENT  IS DIFFERENT  FROM FLOW  FROM FLOW  FROM FLOW FROM FLOW RATE  RATE Q₂  RATE Q₂  RATE Q₂  Q₂ DURING  DURING  DURING DURING  PULL-UP  PULL-UP  PULL-UP  PULL-UP INHIBITOR — — — —

[0169] TABLE 6 FLOW RATE RATIO APPEARANCE RESULTS OF IMAGE (Q₁/Q₂)(SOLVENT STAIN) EVALUATION  0.05 Δ Δ 0.1 ◯ ◯ 0.2 ⊚ ⊚ 0.3 ⊚ ⊚ 0.4 ⊚ ⊚ 0.5⊚ ⊚ 0.6 ⊚ ⊚ 0.7 ⊚ ⊚ 0.8 ◯ ⊚ 1.0 Δ Δ 1.1 Δ Δ COMPARATIVE Δ Δ EXAMPLE 1

[0170] As is evident from TABLE 6, the effect of the present inventionis valid when the circulation volume was changed in the vessels otherthan the vessel used for the degreasing step. Excellent image evaluationresults could be obtained especially when the ratio of the circulationrates are high, for example at a ratio of 0.8.

Example 4

[0171] The same substrate as used in Example 1 was cleaned by the sameconditions as shown in TABLE 7, wherein the kinds of the silicate saltswere changed as shown in TABLE 8. A rejection type electrophotographicphotosensitive member was manufactured and evaluated by the same methodas in Example 1. The results are shown in TABLE 8. TABLE 7 TREATINGDEGREASING RINSE-1 RINSE-2 DRYING CONDITIONS SOLUTION IN PURE WATER PUREWATER PURE WATER PURE WATER THE VESSEL CONTAINING (10 MΩ · CM) (10 MΩ ·CM) (10 MΩ · CM) NONIONIC DETERGENT LIQUID 40° C. 25° C. 25° C. 45° C.TEMPERATURE TREATMENT 5 MINUTES 1.5 MINUTES 1 MINUTE 1 MINUTE TIME OTHER·ULTRASONIC — — — CONDITIONS  TREATMENT ·SHOWER OF  DETERGENT ·Q₁/Q₂ =0.5 INHIBITOR — — — —

[0172] TABLE 8 RESULT OF IMAGE EVALUATION SILICATE POTASSIUM SILICATE ⊚SALT SODIUM SILICATE ◯ MAGNESIUM SILICATE ◯

[0173] As is evident from TABLE 8, good results could be obtained byusing any silicate salts in the table. However, a best result could beobtained by using potassium silicate.

Example 5

[0174] The same substrate as used in EXAMPLE 1 was used and thesubstrate was cleaned by the conditions shown in TABLE 7 as in Example4. The concentration of potassium silicate represented by percentage byweight (wt %) fed to each vessel was changed as shown in TABLE 9, andthe presence of stains on the surface of the substrate was observed bythe naked eyes. Then, a rejection type electrophotographicphotosensitive member was manufactured and evaluated by the same methodas in Example 1. The results are listed in TABLE 9 and thereaftertogether with the results in Example 6. TABLE 9 POTASSIUM SILICATEAPPEARANCE EVALUATION RESULTS (WT %) (SOLVENT STAIN) OF IMAGE 1 0.03 Δ ΔΔ Δ 2 0.05 ◯ ⊚ ◯ ⊙ 3 0.1 ⊚ ⊚ ⊚ ⊚ 4 0.3 ⊚ ⊚ ⊚ ⊚ 5 0.6 ⊚ ⊚ ⊚ ⊚ 7 1.3 ⊚ ⊚ ⊚⊚ 8 1.5 ⊚ ⊚ ⊚ ⊚ 9 2 ◯ ⊚ ◯ ⊚ 10 2.1 Δ Δ Δ Δ

[0175] The results in TABLE 9 show that good results are obtained in theconcentration range of potassium silicate in water of 0.05 wt % or moreand 2.0 wt % or less.

[0176] The substrate was cleaned under the conditions as shown inExample 5, except that an ultrasonic wave was used in the rinsing step-1in which a cleaning solution supplemented with an inhibitor was used.The concentration of potassium silicate was also changed as in Example5, and an electrophotographic photosensitive member was manufactured andevaluated by the same method as in Example 1. The results are also shownin TABLE 9.

[0177] It was confirmed from TABLE 9 that using an ultrasonic wave informing a coating film is effective for the present invention.

Example 7

[0178] The substrate was subjected to the degreasing, rinsing and dryingsteps by the same method as in Example 4, except that aluminumsubstrates in which the Si contents were changed as shown in TABLE 10were used and the silicate salt was potassium silicate. Anelectrophotographic photosensitive member was manufactured and evaluatedby the same method as in Example 1. The results are shown in TABLE 10.TABLE 10 RESULT OF IMAGE Si CONTENT (wt %) EVALUATION EXAMPLE 8 1 0.001◯ 2 0.002 ⊚ 3 0.04 ⊚ 4 0.08 ⊚ 5 0.53 ⊚ 6 0.72 ⊚ 7 0.99 ⊚ 8 1.0 ◯ 9 1.13Δ

[0179] As is evident from TABLE 10, a substrate evaluated to provide agood image can be obtained even when the content of Si in the substrateis changed within the range of 0.001 wt %≦Si≦1 wt %.

Example 8

[0180] A rejection type photoelectric photosensitive member wasmanufactured and evaluated by the same method as in Example 7, exceptthat the content of Fe was changed as shown in TABLE 11. The results areshown in Table 11. TABLE 11 RESULT OF IMAGE Fe CONTENT (wt %) EVALUATIONEXAMPLE 9 1 0.001 ∘ 2 0.003 ⊚ 3 0.04 ⊚ 4 0.08 ⊚ 5 0.48 ⊚ 6 0.61 ⊚ 7 0.99⊚ 8 1.0 ∘ 9 1.13 Δ

[0181] As is evident from TABLE 11, a substrate evaluated to provide agood image can be obtained even when the content of Fe in the substrateis changed within the range of 0.001 wt %≦Fe≦1 wt %.

Example 9

[0182] A rejection type photoelectric photosensitive member wasmanufactured and evaluated by the same method as in Example 7, exceptthat the content of Cu was changed as shown in TABLE 12. The results areshown in Table 12. TABLE 12 RESULT OF IMAGE Cu CONTENT (wt %) EVALUATIONEXAMPLE 8 1 0.001 ∘ 2 0.003 ⊚ 3 0.03 ⊚ 4 0.09 ⊚ 5 0.46 ⊚ 6 0.58 ⊚ 7 0.99⊚ 8 1.0 ∘ 9 1.11 Δ

[0183] As is evident from TABLE 12, a substrate evaluated to provide agood image can be obtained even when the content of Cu in the substrateis changed within the range of 0.001 wt %≦Cu≦1 wt %.

Example 10

[0184] An aluminum substrate in which the contents of Si, Fe and Cu werechanged as shown in TABLE 13 were used and cleaned by the same method asin Example 7. A rejection type electrophotographic photosensitive memberwas manufactured and evaluated by the same method as in Example 1. Theresults are shown in TABLE 13. TABLE 13 Si CONTENT (wt %) RESULT OFIMAGE Si Fe Cu EVALUATION EXAMPLE 1 0.003 0.003 0.004 ∘ 11 2 0.004 0.0050.002 ⊚ 3 0.001 0.02 0.005 ⊚ 4 0.01 0.03 0.005 ⊚ 5 0.03 0.001 0.04 ⊚ 60.02 0.05 0.1 ⊚ 7 0.25 0.20 0.01 ⊚ 8 0.3 0.3 0.4 ∘ 9 0.4 0.4 0.4 Δ

[0185] As is evident from TABLE 13, a substrate evaluated to provide agood image can be obtained even when the contents of Si, Fe and Cu inthe substrate are changed within the range of 0.001 wt %≦Si+Fe+Cu≦1 wt%.

Example 11

[0186] The surface of a cylindrical substrate composed of aluminum,containing 0.03 wt % of Si, 0.03 wt % of Fe and 0.04 wt % of Cu, with adiameter of 108 mm, a length of 358 mm and a wall thickness of 5 mm wasmachined by the same procedure as in Example 1 of the method formanufacturing the electrophotographic photosensitive member according tothe present invention. Fifteen minutes after completing the machiningstep, the surface of the substrate was cleaned under the conditions asshown in TABLE 14. Then, a rejection type electrophotographicphotoconductive member having a layer structure as shown in FIG. 5A wasdeposited on the substrate under the conditions shown in TABLE 15 usinga film deposition apparatus with which a film is deposited by generatinga microwave as show in FIG. 3. The concentration of potassium silicatein water was 0.3 wt %. Electrophotographic characteristics of theelectrophotographic photosensitive member manufactured as describedabove were evaluated with respect to image defects, black spots, andphotographic characteristics 1 and 2. Each evaluation result wasobtained by using 10 pieces each of the photosensitive membersmanufactured by the same deposition condition. TABLE 14 TREATINGCONDITIONS DEGREASING RINSE-1 RINSE-2 DRYING SOLUTION IN PURE WATER PUREWATER PURE WATER AQUEOUS THE VESSEL CONTAINING (10 MΩ·CM) (10 MΩ·CM)CARBON NONIONIC DIOXIDE DETERGENT SOLUTION (20 μS·CM) LIQUID 40° C. 25°C. 25° C. 45° C. TEMPERATURE TREATMENT 5 MINUTES 1.5 MINUTES 1 MINUTE 1MINUTE TIME OTHER ULTRASONIC — — — CONDITIONS TREATMENT SHOWER Q₁/Q₂ =0.4 INHIBITOR — — — —

[0187] TABLE 15 CHARGE INJECTION REJECT LAYER PHOTOCODUCTIVE LAYERSURFACE LAYER KIND OF GAS AND FLOW RATE SiH₄ (sccm) 400 400→450→450186→169→30→25 H₂ 800 800→4300→43000 B₂H₆ (sccm) 1500 1.25 (RELATIVE TOSIH₄) NO (sccm) 6.5 CH₄ (sccm) — INNER PRESSURE (× 10⁴ Pa) 3.83.7→7.3→7.3 4.0→5.98 POWER (W) 200 320→700→700 250 TIME (MIN) 34 INITIAL10 + 350  31

[0188] The appearance of the electrophotographic photosensitive membermanufactured was evaluated by a visual observation of film peeling.Then, the process speed was changed in a range of 200 to 800 mm/sec inthe experiment. A latent image was formed on the surface of theelectrophotographic photosensitive member, subjected to coronaelectrification from a charging device at an applied voltage of 6 to 7kV, by exposure to a laser beam with a wavelength of 788 nm. Thephotosensitive member was placed in a copy machine (NP 6650 made byCanon Co.), reformed so as to be able to print the image on a transferpaper by a conventional copying process, and image quality wasevaluated. The results are listed in TABLE 16 together with the resultsof Comparative example 1. Images were evaluated by the following method.

[0189] Image samples in which image defects appear most frequently amongthe test images, obtained by copying totally half-tone printing mattersand typescripts while changing the process speed, were selected forevaluation. The evaluation method comprises observing over the imagesample with a magnification glass to count the number of white dots in aunit area. The evaluation results are represented in the table using thefollowing four marks:

[0190] {circle over (∘)}: very good;

[0191] ◯: good, very fine white dots are locally observed;

[0192] Δ: fine defects are observed on the overall surface, but thereare no practical problems in recognition of letters; and

[0193] x: there are so many defects that a part of letters are hardlyrecognized.

[0194] An image was printed by changing the process speed so thataverage concentration of the image obtained by placing a totallyhalf-tone printed matter on a copy table becomes 0.4±0.1. An imagesample having most evident stains was selected among the images obtainedas described above and its image quality was evaluated. The presence ofblack spots was visually evaluated of observing the image at a distanceby 40 cm apart from the image. The image was evaluated based on thefollowing criteria and the results are described in the table by thefollowing four marks:

[0195] {circle over (∘)}: very good, no black spots are observed on anyof the copy;

[0196] ◯: good, although quite a few black spots are observed, they arevery weak and cause no problems;

[0197] Δ: Although black spots are observed on every copy they are soslight that there are no practical problems; and

[0198] x: large black spots are observed on all copies.

[0199] The surface potential of the photosensitive member obtained atthe development position when the same electrification voltage wasapplied at a conventional process speed is evaluated by relativeelectrification ability, wherein the electrification ability of theelectrophotographic photosensitive member obtained in ComparativeExample 1 is defined to be 100%.

[0200] Luminous energy, obtained when the potential of thephotosensitive member is decreased to a prescribed level by lightirradiation after applying the same electrification voltage at aconventional process speed, is evaluated as a relative sensitivity,wherein the electrification ability of the electrophotographicphotosensitive member obtained in Comparative Example 1 is defined to be100%. TABLE 16 IMAGE BLACK ELECTROPHOTOGRAPHIC ELECTROPHOTOGRAPHICDEFECT SPOT CHARACTERISTICS 1 CHARACTERISTICS 1 EXAMPLE 1 ⊚ ⊚ 132% 122%COMPARATIVE ∘ ∘ 100% 100% EXAMPLE 1

[0201] TABLE 16 shows very good evaluation results, indicating that theelectrophotographic characteristics are improved.

Example 12

[0202] A rejection type electrophotographic photosensitive membermanufactured by the same method as in Example 11 using the samesubstrate as in Example 11 was evaluated by the following method. Theresults are shown in TABLE 17 together with the results in Comparativeexample 1.

[0203] A piezo element suffering an arbitrary load is used as a blade,and the tensile force applied to the blade from the drum before andafter initiation of drum rotation is detected as a frictional force. Themaximum coefficient of static friction was calculated from the load andmaximum static friction force, and the maximum coefficient of kineticfriction was calculated from the kinetic friction force duringstationary rotation of the rotor. The coefficient was relativelyevaluated by defining the value in Comparative Example 1 to be 100% (thelower ratio indicates better lubricancy).

[0204] A sheet of A3 size section paper (made by Kokuyo Co.) was placedon the copy table. The degree of exposure on the section paper wasadjusted within a range from the degree when lines on the section paperare hardly recognizable to the degree when fog of white spaces in thesection paper starts to be visualized by changing the diaphragm apertureof the copy machine. Ten copies with various copy densities wereprinted.

[0205] These images were visually observed at a distance of 40 cm apartfrom the image to confirm if differences among the densities could berecognized. The results were evaluated by the following criteria shownin the table by four marks:

[0206] {circle over (∘)}: very good, no irregular images are observed onany of the copies;

[0207] ◯: irregular images are observed on some copies but not observedon the other copies. The degree of irregularity is so slight that thereare no problems;

[0208] Δ: while irregular images are observed on every copy, the degreeof irregularity is so slight that there is no practical problem; and

[0209] x: large irregular images are observed on all the copies.

[0210] Image samples obtained by placing a conventional typescriptcomprising letters only on white paper on the copy table were visuallyobserved to evaluate the degree of fog of white images. The results wereevaluated by the following four marks.

[0211] {circle over (∘)}: very good;

[0212] ◯: good, fog is observed on a few portions of the image;

[0213] Δ: fog is observed all over the image, but letters arerecognizable without any problem; and

[0214] x: letters are hardly recognizable because of fog at some portionof the image. TABLE 17 IRREGULAR FOG OF LUBRICANCY IMAGE WIHITE IMAGEEXAMPLE 12 130% ⊚ ⊚ COMPARATIVE 100% ∘ ∘ EXAMPLE 1

[0215] TABLE 17 clearly shows that the evaluation results are very good.

[0216] After subjecting the same substrate as used in Example 11 to asurface treatment by the method as in Example 11, a rejection typeelectrophotographic photosensitive member as shown in FIG. 5B wasmanufactured under the conditions as shown in TABLE 18 using a μw PCVDapparatus that is a film deposition apparatus for depositing a film bygenerating a microwave as shown in FIG. 3A and FIG. 3B. The results ofevaluation by the method as in Example 11 are shown in TABLE 19. Thedegreasing, rinsing and drying treatments shown in Comparative Example 1were applied to the substrate and the rejection type electrophotographicphotosensitive member shown in FIG. 5B was manufactured by theconditions as shown in TABLE 18. The evaluation results are also shownin TABLE 19. The reference numerals 501, 502, 503-1 and 503-2, and 505denote an aluminum substrate, a charge injection reject layer, a chargetransfer layer, a charge generation layer and a surface layer,respectively. The characteristics of the electrophotograph manufacturedaccording to this example were evaluated relative to the characteristicsof the electrophotograph manufactured according to Comparative Example 1defined to be 100%.

[0217]FIG. 3A shows a side view for describing the microwave CVDapparatus, wherein the reference numeral 301 denotes a chamber forhousing the substrate 306, the reference numeral 302 denotes a motor forallowing the substrate 306 to rotate for depositing a film on thesurface of the substrate 306, the reference numeral 303 denotes a heaterfor heating the substrate 306 for depositing a film, the referencenumeral 304 denotes an evacuation path for evacuating the chamber 301,and the discharge space 407 is a space between the substrate 306 and theelectrode 308.

[0218] A direct current electric power is supplied to the electrode 308with a electric power supply device 309.

[0219] The electrode 308 also serves as an inlet tube for introducing agas into the chamber 301.

[0220] The reference numeral 310 denotes a microwave guide window forintroducing a microwave conducting through the guide path 311 into thechamber 301.

[0221]FIG. 3B shows a cross section along the line X-X of the microwaveCVD apparatus in FIG. 3A. TABLE 18 CHARGE INJECTION CHARGE CHARGEREJECTION TRANSFER GENERATION SURFACE LAYER LAYER LAYER LAYER FLOW RATEOF MATERIAL GAS SiH₄ 360 sccm 360 sccm 360 sccm 70 sccm He 100 sccm 100sccm 100 sccm 100 sccm CH₄ 40 sccm 40 sccm 40 sccm 350 sccm PRESSURE1000 ppm 0 ppm 0 ppm 0 ppm MICROWAVE 1.4 Pa 1.4 Pa 1.33 Pa 1.6 Pa BIASVOLTAGE 1000 W 1000 W 1000 W 1000 W FILM 100 V 100 V 100 V 100 VTHICKNESS 3 μm 200 μm 5 μm 0.5 μm

[0222] TABLE 19 IMAGE BLACK ELECTROPHOTOGRAPHIC ELECTROPHOTOGRAPHICDEFECT STAIN CHARACTERISTICS 1 CHARACTERISTICS 1 EXAMPLE 12 ⊚ ⊚ 135%128% COMPARATIVE ∘ ∘ 100% 100% EXAMPLE 1

[0223] The present invention is valid for different apparatus and layerconstructions as is evident from TABLE 19.

Example 14

[0224] After subjecting the same substrate as used in Example 11 to thesame surface treatment as in Example 11, a rejection typeelectrophotographic photosensitive member having the layer structure asshown in FIG. 5B was manufactured by the conditions shown in TABLE 20using a VHF PCVD apparatus 421 that is a film deposition apparatus fordepositing a film using a VHF band wave shown in FIG. 4. Thephotosensitive member was evaluated and good results as in Example 11were obtained.

[0225] In FIG. 4, the reference numeral 422 denotes a motor for allowingthe substrate 426 to rotate for depositing a film on the surface of thesubstrate 426, the reference numeral 423 denotes a heater for heatingthe substrate 426 for depositing the film, the reference numeral 424denotes an evacuation path for evacuating the evacuation space 427 thatis a space between the substrate 426 and an electrode 425, and thereference numeral 428 denotes a high frequency wave matching box.

[0226] A material gas introduction tube (not shown) and an electrode 425are provided in the apparatus, and the high frequency wave matching box428 is connected to the electrode 425. The discharge space 427 isconnected to a diffusion pump (not shown) through the evacuation tube424.

[0227] A VHF electric power is applied to the discharge space 427through the high frequency matching box 428 by setting, for example, aVHF power source (not shown) with a frequency of 500 MHz at a desiredelectric power after the pressure has been stabilized by evacuation togenerate a glow discharge in the apparatus. The material gas introducedinto the discharge space 427 surrounded by the substrates 426 isdissociated by being excited with the discharge energy, depositing aprescribed film on the substrate 426.

[0228] The apparatus shown in FIG. 4 is suitable for massproductionsince it is able to simultaneously manufacture plural photosensitivemembers as the apparatus shown in FIG. 3 can. TABLE 20 CHARGE INJECTIONREJECT LAYER PHOTOCODUCTIVE LAYER SURFACE LAYER KIND OF GAS AND FLOWRATE SiH₄ (sccm) 200 200→240 200→10→10 H₂ 660 660→960 B₂H₆ (sccm) 1500 3(RELATIVE TO SiH₄) NO (sccm) 10 CH₄ (sccm) SiF₄ INNER PRESSURE (× 10³Pa) 4.0 4.0 2.0 POWER (W) 200 200→60O 250 TIME (MIN) 2.5 28 0.5

[0229] As described above, impurities removed from the substrate bycleaning can be prevented from adhering on the cleaning subject again toimprove the cleaning effect, by making the circulation flow rate of thecleaning liquid during pull-up of the substrate larger than thecirculation flow rate when the cleaning subject is dipped in the liquidin the cleaning method of the surface of the cleaning subject. Theeffect for preventing impurities from adhering again becomes evidentespecially when the surface of the substrate is cleaned in advance todeposition of a film in the method for manufacturing anelectrophotographic photosensitive member in which a functional film isdeposited on an aluminum substrate by a plasma CVD method. Using aliquid containing an inhibitor to form an Al—Si—O coating film on thesurface of the substrate allows a high quality film to be deposited onthe surface of the substrate, thereby enabling a uniform and highquality of electrophotographic photosensitive member to be constantlyproduced with a cheap production cost.

What is claimed is:
 1. A method for cleaning a cleaning subject byallowing a liquid filled in a vessel to overflow, wherein the cleaningsubject is cleaned by pulling up the cleaning subject from the liquidfilled in the vessel while allowing the liquid to overflow from thevessel, or wherein the cleaning subject is cleaned by pulling up thecleaning subject from the liquid while increasing the flow rate of theoverflowing liquid.
 2. A cleaning method according to claim 1 , whereinthe liquid is circulating between the vessel and outside of the vessel.3. A cleaning method according to claim 1 satisfying the followingequation, wherein Q₁ denotes the flow rate of a liquid when the cleaningsubject is dipped in the liquid and Q₂ denotes the flow rate of a liquidwhen the cleaning subject is cleaned by pulling up the cleaning subjectfrom the liquid filled in the vessel: 0.1≦Q ₁ /Q ₂≦0.8
 4. A cleaningmethod according to claim 1 carried out at least in one step comprising:degreasing oil components adhered on the cleaning subject; rinsing thecleaning object after the degreasing step; and drying the cleaningsubject after the rinse step.
 5. A cleaning method according to claim 1, wherein showering water is sprayed by showering means to the cleaningsubject pulled up out of the liquid.
 6. A cleaning method according toclaim 1 , wherein the liquid contains a surfactant.
 7. A cleaning methodaccording to claim 1 , wherein the liquid contains an inhibitor forprotecting the surface of the cleaning subject.
 8. A cleaning methodaccording to claim 7 , wherein the inhibitor is a silicate salt.
 9. Acleaning method according to claim 8 , wherein the inhibitor is apotassium silicate.
 10. A cleaning method according to claim 9 , whereinthe solution contains potassium silicate in the range of 0.05 wt % ormore and 2 wt % or less.
 11. A cleaning method according to claim 1 ,wherein the solution contains carbon dioxide.
 12. A cleaning methodaccording to claim 1 , wherein the liquid is pure water.
 13. A cleaningmethod according to claim 1 , wherein the cleaning subject is cleaned byirradiating an ultrasonic wave to the cleaning subject with anultrasonic wave generating means.
 14. A cleaning method according toclaim 1 , wherein the liquid is circulated while allowing the liquid tooverflow at the flow rate of the liquid in the circulation step.
 15. Acleaning method according to claim 1 , wherein the cleaning subject is asubstrate for an electrophotographic photosensitive member.
 16. Acleaning method according to claim 1 , wherein the cleaning subject ispulled up from the liquid while preventing the overflowed liquid fromadhering on the surface of the cleaning subject again.
 17. A cleaningmethod according to claim 1 , wherein the cleaning subject is aconductive material.
 18. A cleaning method according to claim 17 ,wherein the conductive material is aluminum.
 19. A cleaning methodaccording to claim 18 , wherein the aluminum material contains 10 ppm ormore and 1 wt % or less of iron.
 20. A cleaning method according toclaim 18 , wherein the aluminum material contains 10 ppm or more and 1wt % or less of silicon.
 21. A cleaning method according to claim 18 ,wherein the aluminum material contains 10 ppm or more and 1 wt % or lessof copper.
 22. A cleaning method according to claim 18 , wherein thecombined content of iron, silicon and copper in the aluminum material ismore than 0.01 wt % and 1 wt % or less.
 23. A method for manufacturingan electrophotographic photosensitive member, wherein theelectrophotographic photosensitive member is manufactured by machiningthe cleaning subject cleaned by the cleaning method according to claim
 1. 24. An electrophotographic photosensitive member obtained by machiningthe cleaning subject cleaned by the cleaning method according to claim
 1. 25. A cleaning apparatus of a cleaning subject comprising a vessel forfilling a liquid, a flow rate control means for allowing the liquid tooverflow from the vessel, a circulation means for feeding the overflowliquid to the vessel again, and a vessel provided between the vessel andliquid circulation means.
 26. A cleaning apparatus of a cleaning subjectaccording to claim 25 , wherein the circulation means feeds thecollected liquid to the vessel from the bottom of the vessel.
 27. Amethod for cleaning the substrate by allowing a liquid filled in avessel to overflow, wherein the substrate is cleaned by pulling up thesubstrate from the liquid filled in the vessel while allowing the liquidto overflow from the vessel.
 28. A method for cleaning a substrate byusing a liquid which is contained by a vessel, comprising steps of: thefirst overflowing step, wherein the liquid is allowed to be overflowedfrom the vessel while the substrate is immersed in said liquid containedby the vessel, the second overflowing step, wherein the liquid isallowed to be overflowed from a vessel while the substrate is pull up insaid liquid contained by the vessel, wherein a flow rate of theoverflowing liquid of the second overflowing step is higher than a flowrate of the overflowing liquid of the first overflowing step.